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<br />highest manganese detections recorded for surface water monitoring were in water <br />collected from station location RS-3 situated on the southern permit boundary in an <br />intermittent tributary flowing to the Rito Seco (CDMG, 1994). Manganese detections were <br />consistently higher at the RSA location and, though the flow rate of the tributary is very <br />low, it may contribute to the elevated levels of manganese &t downstream locations RS-2 <br />and RS-5 (Table 3; Attachment 1). <br />Iron concentrations (total) in samples collected at the RS-1 location prior to the <br />commencement of current operations ranged from 0.01 mg/L to 0.41 mg/L Iron <br />concentrations in samples collected from the RS-5 location, downstream of site <br />operations, on August 20 and November 2, 1988 were 1.2 and 0.56 mg/L, respectively. <br />These concentration were equal to or greater than three times the corresponding iron <br />concentration detected in samples collected from the RS-1 on those dates (Attachment <br />1). <br />Geology and Hydrogeology <br />The area of the site is on the edge of the San Luis Basin eastward tilling graben (CDMG, <br />1990). Stratigraphy in the sfte vicinity is comprised of four basic units described from the <br />surface: quantemary alluviumf alluvial fan material; tertiary Santa Fe Conglomerate (USGS, <br />1979); precambran pink granitic gneiss; and biotRe/biotke-amphibole gneiss (BMG, 1988; <br />BMG, 1994). Local ground water underlying the site occurs in the Santa Fe <br />Conglomerate and the Precambrian biotite and biotite-amphibole gneiss ore zone (BMG, <br />1988). Refer to the SAP (MK, 1995) for a more detailed discussion of the geologic <br />setting. <br />Site Hydrology <br />The Rito Seco River flows adjacent to site operations. Rito Seto River flow is diverted via <br />a ditch into the Salazar Reservoir approximately 2 miles downstream. Two miles <br />downstream of the Salazar Reservoir, the Rito Seco River drains into Culebra Creek. The <br />remainder of the 15-mile target distance limit occurs within Culebra Creek (USGS, 1983). <br />Flow gaging recorded in 1988 at Station RS-1, located on the Rito Seoo River at the <br />western edge of site operations, documented a monthly flow rate ranging from 4.6 to 8.8 <br />cubic feet per second (cfs)(BMG, 1988). Rito Seto River water pH measuremerrts <br />recorded during SI field activities ranged from 7.37 (upstream of site operations) to 8.69 <br />(adjacent to Salazar Res.) standard units. Physical parameters of Rfto Seto water <br />measured at sample locations during 51 field activities are summarized below: <br />mo~:eoq~mravmnt - 3 - mR a or/+am~ <br />